1. to find their + and - you can use a volt meter to find out by touching the terminals in the led soldered on the PSP.
2. i wouldnt bother with that one since you have trouble finding + and - no offence.
3. i never used resistors with my leds on my psp's i had in the past, so no need to bother.
4. there are many diagrams on google with the + and - labeled on the board. just search "positive and negative terminals on psp board".